12. c3d5 This allows Black to play f7-f5. 12... f7f5  13. d5b6 White takes the chance to complicate the game. To be honest, when I first looked at the position my impression was that Black had a big advantage and that some very strong sequence should be possible. This is not the case: the game is balanced. 13... f5g4  14. b6a8 